1. Field of the Invention
The present invention relates to technology for correcting keystone distortion for a projector.
2. Description of the Related Art
In recent years, projectors for which a video image is projected on a screen have rapidly become popular. Generally, projectors are designed with a prerequisite of being placed directly opposite the screen, so when the projector is not placed directly opposite the screen, the image becomes distorted.
Meanwhile, when the projector is not placed directly opposite the screen, not only the image, but also the brightness distribution fluctuates. Furthermore, when equipping the projector with an image capturing device, the imaging distance differs at the sides of the screen, so even according to the inverse square theorem, at the sides of the screen, there will be fluctuation in the received light amount of the imaging device. This kind of fluctuation in light receiving amount may also be used for estimating the slope of the screen in relation to the light axis of the projector.
However, there is the problem that the fluctuation in the light receiving amount fluctuates not only with the slope of the screen, but also according to the light intensity distribution when the projector is placed directly opposite the screen.